Meaning of reference values in Diagbox?

[max1]

Sorry for my multiple threads lately but just a quick question! In Diagbox there are few places where there are 'reference values' & i don't know what these mean or where they come from ? I've scanned the car on different days this past week & am getting different values each time for 'coolant temp reference value'. The 'coolant temp' stays pretty much the same at around 10c but the 'coolant temp reference value' has changed from -48c on one day to now 104c ? I still have a no start & no codes & am trying to find any anomalies & this seems pretty suspect!? This is it from the other day reading -48:

Also while I'm here what does anyone think about using easy start spray ? A lot of people seem to advise against it as it might damage the MAF sensor, but it would be useful for me as i don't have a test gauge & want to try & rule out a fuel problem.

thanks

[GiveMeABreak]

The reference values should show what a particular reading is expected to be under the current conditions the engine is running under.

So the reference value may change based on for example when the engine is cold, as opposed to when it is at operating temperature, so you can compare the reference value to what a sensor is actually returning given the current running conditions.

[max1]

Thanks for this really helpful. So in this instance where I am just cranking & on one day i have a reference value of -48 & then on another day its reading +104, would this suggest a fault somewhere? Perhaps external wiring or maybe internal damage to the ECU ? Im not sure but from your description the reference value is derived from other sensors around the car & not the coolant temp sensor? If so do you know which ones might be involved so i can try & narrow the problem down a bit ?

thanks

[xantia_v6]

It is possible that diagbox is giving a false reading and you are just seeing a random number which does not indicate any problem with your car. I would not put any effort into trying to fix such a problem without other evidence of a fault.

[GiveMeABreak]

The reference values should be direct from the ECU in question, but yes I wouldn’t stress over it unless you have a fault code or an engine dash light warning.

[MikeT]

Max, note in the pic you posted Diagbox already provides details on the highlighted parameter "Engine Speed" below in the white box.
Just scroll down and highlight the Coolant parameter you're interested in.

[max1]

Thanks for the info. The white box doesn't give any info for that unfortunately Mike.